Customers or potential purchasers of software programs often desire to test the programs before determining whether or not to purchase them. This may occur because written literature does not adequately provide the customer with a feel for the functionality of the software program when in operation. The written literature simply describes the program, and customers often want to actually work with the software program in order to determine if they want to buy the program.
Some software vendors provide demonstration programs of their software programs for sale. These demonstration programs are not the fully operating version of the software program. The demonstration program simply contains some of the functionality of the full software program in order to provide the customer with a feel for the functionality of the program. Since the demonstration version is not a fully operating version of the program, however, it does not provide a customer with a complete picture of the program's functionality. Therefore, demonstration versions are limited in how they may assist a customer in deciding whether to purchase a particular software program.
Recently, some software vendors are providing fully operating versions of software programs which a customer may sample. These software programs are intended to be securely stored on a particular storage medium. Therefore, when a customer samples a fully operating version of a program, the program being sampled is securely maintained by another program which seeks to prevent the customer from obtaining a free copy of the sampled program.
These software vendors typically distribute the programs to be sampled on some type of transportable storage medium. For example, a software vendor may provide a floppy diskette on which is contained the program to be sampled. The diskette may be locked due to changes to the physical storage medium such that the customer may not obtain a free copy of the program. Other software vendors provide a CD-ROM which stores a large number of programs which may be sampled. The CD-ROM also contains a program which manages and in effect supervises the sampling of the programs such that a customer may not obtain copies of the programs without first purchasing them and obtaining particular unlocking codes.
These distribution systems for sampling fully operating versions of programs, however, are generally limited in that they do not provide for on-line distribution. These systems typically distribute the programs on some type of transportable storage medium, such as a CD-ROM or hard disk drive sold with a computer. This type of distribution can be more burdensome to the computer user, because an on-line distribution channel is more easily accessible, since the computer users need simply "dial up" a network or bulletin board.
These systems for providing the sampling of fully operating versions of programs are also limited in the security provided to the programs being sampled. For example, they typically prevent unauthorized copying of programs by dividing the program or removing portions of the program such that a secure "key" is required to reassemble the program and thus operate it. These methods, however, require that one tamper with the program, which can make the program unstable. In addition, these methods typically do not work with all applications. For example, some applications use a checksum program to prevent damage from computer viruses. These distribution methods change the format of the program, which can result in the checksum virus check incorrectly returning a error or message that the program is corrupted.